<!DOCTYPE html>
<html xmlns:v-bind="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8">
    <title>if</title>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>

<body>
<div id="app">


    <!--<div v-show="flag">hello javaboy!</div>-->
    <div v-if="flag">hello javaboy!</div>


</div>


</body>


<script>
    var app = new Vue({
        el: '#app',
        data: {
            flag: true

        }
    })

</script>
</html>
